Back ticks in titles (incorrectly?) converted to hypens

[bduncanj]

Smashing library, much thanks!

I may be abusing markdown a little, but I'm using code back ticks in my titles:

## Messages
### `system-alarm-start`
### `system-alarm-end`

This however produces HTML in which the backtick is replaced with a hyphen in the id attribute of the resulting header element:

<h2 id="messages">Messages</h2>
<h3 id="-system-alarm-start-"><code>system-alarm-start</code></h3>
<h3 id="-system-alarm-end-"><code>system-alarm-end</code></h3>

The problem is that I'm using marked-toc to convert this into the following markdown TOC (and then HTML via marked) which of course is now incompatible as that package just ignores the back ticks in the headers:

* [Messages](#messages)
  * [`system-alarm-start`](#system-alarm-start)
  * [`system-alarm-end`](#system-alarm-end)

... and finally ...

<ul>
<li><a href="#messages">Messages</a><ul>
<li><a href="#system-alarm-start"><code>system-alarm-start</code></a></li>
<li><a href="#system-alarm-end"><code>system-alarm-end</code></a></li>
</ul>
</li>
</ul>

[Feder1co5oave]

I, too, rely heavily on hashes.

The naive solution is to override the heading renderer and generate ids in the same way marked-toc does.

See related issues #432 #450. The problem extends far beyond leading/trailing slashes.
I think I proposed a reasonable solution in #456. Feel free to merge it. Notice that you can then override the heading renderer and possibly use uslug to generate id attributes.

[F1LT3R]

+1 to fixing this out of the box

[franciscop]

+1. I'd go a bit further and say that leading/trailing hyphens should be removed as well:

# Hello!
# How to fix X?

<h1 id="hello-">Hello!</h1>
<h1 id="how-to-fix-x-">How to fix X?</h1>

[joshbruce]

#981